(CNN)Almost everyone on Earth now breathes polluted air, according to an air quality map released Tuesday by the World Health Organization.

The interactive map, based on global air pollution data, confirms that 92% of the world's population lives in places where outdoor air quality fails to meet WHO guidelines.

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This is a concerning public health issue, as air pollution can harm your lungs, heart and even brain -- with the potential to cause premature death, said Dr. Maria Neira, director of the organization's Department of Public Health, Environmental and Social Determinants of Health.

Just how deadly is air pollution? About 3 million deaths each year can be linked to exposure to outdoor air pollution, according to the WHO.

"What is still surprising is the fact that we have been alerting about these horrible figures for a while now, and it's not improving," Neira said.From 2008 to 2013, global urban air pollution levels rose by 8%, despite improvements in some regions, according to the WHO.

Dirty air around the world

The new WHO map was created with data on the annual amount of particulate matter, or PM, found in the air around the world. PM is a type of air pollutant that consists of small particles, from tiny molecular clusters to the dust or pollen that we can see. For instance, PM2.5 has a diameter of fewer than 2.5 micrometers, and PM10 is about one-seventh the thickness of human hair.

WHO: 4 in 5 city dwellers live in overpolluted urban areas

Data were collected from 2008 to 2015 using satellite measurements, air transport models and ground-station monitors based in more than 3,000 locations in 103 countries.

"With more accurate methodology and satellite information and better calculation of the estimates and using the standards, now we can be more confident in the data," Neira said.

PM measurements were used to build the map because particulate matter includes different pollutants, it is universally present around the globe and it poses a public health risk, she said.

According to WHO air quality guidelines, levels ofPM2.5 -- the most dangerous kind of PM -- should be limited to 10 micrograms per cubic meter. However, the new map revealed that a whopping 92% of the world's population lives in places where air quality exceeds that threshold.

A new map of annual levels of PM2.5, released by the World Health Organization on Tuesday.

PM2.5 includes pollutants such as sulfate, nitrates and black carbon, which can sneak deep into the lungs and cardiovascular system.

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Separate studies have shown associations between increased PM2.5 levels and increased risk of mortality and morbidity, said Jim Zhang, professor of global and environmental health at Duke University's Nicholas School of the Environment and the Duke Global Health Institute. He was not involved in the new WHO map.

"We also have data to show how PM2.5 affects the lung and the cardiovascular health. For example, PM2.5 exposure increases tissue and systemic inflammation, increases oxidative damage to DNA and cell membrane lipids, increases the risk for thrombosis," he said. "We also started to see cumulating evidence that PM2.5 lowers birth weight and impairs metabolic, cognitive and immune function."

These smaller particles can enter and deposit deep into your lungs, and cause the most health effects, said Stuart Batterman, professor of environmental health sciences at the University of Michigan, who was not involved with the new WHO map.

"Those health effects can include aggravation or causation of asthma, cardiovascular and respiratory disease, hospitalizations and death," he added.

Where air quality is most alarming

Many of the areas lacking clean air are in the Western Pacific, the Mediterranean region, sub-Saharan countries and Southeast Asia, according to the map.

Nearly 90% of deaths linked to air pollution occur in low- and middle-income countries, and nearly two out of three occur in Southeast Asia and Western Pacific regions, according to the WHO.

Although most sources of air pollution are from human activity, air quality can also be influenced by natural dust and dust storms, found in many desert environments in those regions, according to the WHO.

"Many of the places that have high levels of pollution have very little monitoring data, and this includes countries highlighted in the report, including most of Africa and much of the developing world," Batterman said of the WHO map.

"Air pollution is causing millions of deaths per year, mostly but not exclusively in the developing world, due to very poorly controlled combustion as well as indoor air problems from the use of biomass fuels indoors, such as wood, dung and coal," he said.

Yet much of the developed world shows high levels of PM as well, according to the map. This includes major cities in Europe, such as Paris and London, and those in the United States, such as Los Angeles, New York and Chicago.

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"The pollutants that affect most people in the United States include particulate matter, especially the smallest particles that enter deep into the lungs, and ozone. Ozone has tended to be a problem that has affected large portions of East Coast, Gulf and West Coast," Batterman said. "There's also major regions across the Midwest and elsewhere that have problems with ozone.

"Particulate matter pollution also has been an issue in many different regions," he added. "It is often a problem in some of the more urbanized areas, as well as industrialized areas of the country."

However, in order to move forward in efforts to improve air quality, identifying the type of pollutant in various regions is just as important as identifying the sources of pollution, Neira said.

As China has become richer, it's paid a big environmental price. One in five deaths there are now attributable to poor quality air. The country ranks last among 180 for outdoor air pollution, according to a new report. Half the population lives with air unsafe by international standards. China is choking on its success.

Yale's Environmental Performance Index shows how economic development both improves and hurts the environment. Since the turn of the century, about 410 million people have gained access to clean water for the first time, for instance. Millions more people have sanitation and more of the marine environment is being conserved.

But, at the time time, the world is losing Peru-sized tracts of forests each year, 34% of fish stocks are over-exploited, and air quality is getting worse across East Asia and the Pacific region. Bad air now kills five times as many people as poor water, although the latter tends to get more attention from the development community.

"As nations have become wealthier, particularly in Asia, their governments invest in sanitation infrastructure and fewer people are exposed to unsafe water, leading to fewer deaths from waterborne illnesses," the report says. "But as countries develop, increased industrial production, shipping, and automotive transportation foul the air, exposing human populations to dangerous airborne compounds.

The Index rates countries by their environmental health and "ecosystem vitality," using 20 indicators. European countries perform best. Finland, Iceland, Sweden, Denmark and Slovenia top the list, with the U.S. in 26th place (we've dropped since the last report two years ago) and Brazil in 46th. China is 118th and India is 141st.

Altogether, 3.5 billion people—or about half the global population—live with unsafe air quality. One third of those are in East Asia (including half of South Korea). In India, almost 75% of the population is exposed to dangerous levels of fine particulate matter. In fact, its problem is even worse than China's, though the former is more notorious for its pollution issues.

Wearing inexpensive cloth masks in the hope of reducing exposure to air pollution may be of only a little benefit and give you a false sense of security, especially in highly polluted areas, new research suggests. Washable cloth masks are widely used in India and other Asian countries for personal protection against airborne particulate matter.

“Wearing cloth masks reduced the exposure to some extent,” but “the most commonly used cloth mask products perform poorly when compared to alternative options available on the market,” said the study by scientists at University of Massachusetts Amherst.

“What became clear to us is that millions of people probably wear these masks and feel safer, but we worry that this is potentially making things worse, if they stand next to a diesel truck and think they are protected by the mask, for example,” said one of the researchers Richard Peltier.

In a series of experiments with an experimental mannequin in Nepal, the researchers tested four masks, one pleated surgical type, two cloth and one cone-shaped cloth with exhalation flaps. They tested for several variables and effectiveness in filtering out five different synthetic aerosol particle sizes plus three particle sizes of diluted whole diesel exhaust, which simulated real-world conditions.

Among the cloth masks, the one with exhaust valves performed fairly well, removing 80-90 percent of synthetic particles and about 57 per cent of diesel exhaust. Plain cloth masks were “only marginally beneficial” they said, in protecting people from particles smaller than 2.5 micrometers, often considered more harmful than larger particles because they can penetrate the lungs more deeply.

“Unfortunately, the least effective two mask types are also inexpensive, reusable and are widely used in developing countries, implying they are a popular consumer choice where pollution mitigation is warranted,” the authors noted. Peltier said this study has implications well beyond Nepal, because these masks are very common in China and India, and across much of southeast and southwest Asia.

“This study shows that people should know there is a limit to protection you can get from these cloth masks, but also that something is better than nothing,” Kabindra Shakya, who was part of the research team, pointed out. The findings appeared in the Journal of Exposure Science and Environmental Epidemiology.

Air pollution has become a major contributor to stroke for the first time, with unclean air now blamed for nearly one third of the years of healthy life lost to the condition worldwide.

In an unprecedented survey of global risk factors for stroke, air pollution in the form of fine particulate matter ranked seventh in terms of its impact on healthy lifespan, while household air pollution from burning solid fuels ranked eighth.

Valery Feigin, director of the National Institute for Stroke and Applied Neurosciences at Auckland University of Technology, said that while he expected air pollution to emerge as a threat, the extent of the problem had taken researchers by surprise.

Urgent action needed to stop terrifying rise in air pollution, warns OECD Read more“We did not expect the effect would be of this magnitude, or increasing so much over the last two decades,” he said. “Our study is the first to demonstrate a large and increasingly hazardous effect of air pollution on stroke burden worldwide.”

The result is particularly striking because the analysis is likely to have underestimated the effects of air pollution on stroke, as the impact of burning fossil fuels was not fully accounted for. Emissions from fossil fuels are more harmful to the cardiovascular system than the fine particulate matter the team analysed, Feigin said.

Scientists in the field said the “alarming” finding, published in the journal Lancet Neurology, showed that harm caused by air pollution to the lungs, heart and brain had been underestimated.

About 15 million people a year suffer a stroke worldwide. Nearly six million die, and five million are left with permanent disabilities, such as loss of sight and speech, paralysis and confusion.

Feigin analysed a haul of medical data from the Global Burden of Disease Study 2013 to build a picture of how different risk factors for stroke left people disabled and cut their lives short in 188 countries between 1990 and 2013. The study highlighted the most important contributors to stroke worldwide as high blood pressure, a diet low in fruit, obesity, a high salt diet, smoking, and not eating enough vegetables.

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Nearly three quarters of the global burden of stroke was linked to lifestyle choices, such as smoking, bad diet and too little exercise, suggesting that people can do a lot to reduce their risk of stroke. Meanwhile, ambient air pollution was linked to 17%, and household air quality to 16%, of the burden of stroke, measured by the years of healthy life it reduced. Pollution in homes from burning solid fuel for heat emerged as a risk factor for stroke only in low and middle income countries.

From 1990 to 2013, the global harm caused by stroke due to poor diet, smoking and almost every other risk factor rose, with only secondhand smoke and household pollution falling. Environmental air pollution came from vehicles, power plants, industry and fossil fuels, with traditional burning of biomass a major source in developing countries.

Over the long term, air pollution is thought to increase the risk of stroke by hardening arteries in the brain, making blood thicker and raising blood pressure, so boosting the risk of clots in the brain. But it may have acute effects too, such as rupturing the plaques that build up in arteries, which can then go on to cause blockages.

“As one of the main sources of air pollution is car emissions, staying away from the streets, especially at rush hour, or avoiding busy roads, can help to reduce exposure to air pollution,” said Feigin. On days when air pollution is high, he said people should stay indoors as much as possible.

Air pollution: a dark cloud of filth poisons the world’s cities Read moreThe study follows a report in February from the Royal College of Physicians which blamed air pollution both inside and outside homes for at least 40,000 deaths a year in the UK.

Stephen Holgate, professor of immunopharmacology at Southampton University, who led the Royal College of Physicians report, said it had long been known that air pollution was a driver or cardiovascular disease from work that had focused on heart attacks.

“This impressive international survey now throws into stark relief a major effect of air pollution as a risk factor in stroke,” he told the Guardian. “It adds further to the increasing evidence highlighted by the recent Royal College of Physicians Report showing that air pollution has severe adverse toxic effects at multiple sites in the body from conception to old age. Air pollution is a major public health hazard and demands action to improve air quality both in the developed and developing world.”

In a comment piece that accompanies Feigin’s study, Vladimir Hachinksi at the University of Western Ontario and Mahmoud Reza Azarpazhooh at Mashhad University of Medical Sciences in Iran, stress the global nature of the air pollution problem.

“The most alarming finding was that about a third of the burden of stroke is attributable to air pollution. Although air pollution is known to damage the lungs, heart, and brain, the extent of this threat seems to have been underestimated,” they write. “Air pollution is not just a problem in big cities, but is also a global problem. With the ceaseless air streams across oceans and continents, what happens in Beijing matters in Berlin.”

More and more studies show that the brain and human cognitive development are affected by pollution.

In a new study conducted by a research team at Umeå University, the correlation between exposure to air pollution in residential areas and children' and adolescents' psychiatric health was studied. The study was performed by looking at register-based data, where dispensed medications of all Swedes are registered, together with Swedish National Register data of air pollution concentrations. The entire population under 18 in the Swedish counties of Stockholm, Västra Götaland, Skåne and Västerbotten were studied.

Stockholm, Västra Götaland and Skåne counties are located in the more densely populated parts in the south and contain the three largest cities in Sweden with a population density of between 68 and 338/km2 whereas Västerbotten County lies the north of Sweden with a population density of 5/ km2. The four counties are different not just in terms of geographic location, size and population density but also with respect to migration, socioeconomic characteristics, urbanisation, and air pollution concentrations.

The results show that air pollution increased the risk of having dispensed medication for at least one psychiatric diagnosis for children and adolescents, the risk increased with 9% with a 10 microgram per cubic meter increased concentration of nitrogen dioxide even after socioeconomic and demographic factors were taken into account.

"The results can mean that a decreased concentration of air pollution, first and foremost traffic-related air pollution, may reduce psychiatric disorders in children and adolescents," says researcher Anna Oudin, the Unit for Occupational and Environmental Medicine at the Department of Public Health and Clinical Medicine, who led the study.